1. Field of the Invention
This invention relates to a sorting apparatus adapted to scan the entire surface of articles randomly disposed on a roller conveyor as the conveyor is moved through a viewed area and to classify each article on the basis of surface defects or blemishes.
2. Description of the Prior Art
It is a difficult task to sort relatively large objects for surface defects or blemishes. The problems presented by such a sorting task are different in some respects than those encountered when classifying articles on the basis of their color and reflectivity. For example, it is usually sufficient for a color sort to pass the articles being sorted through a viewed area so that light at predetermined color wavelengths which is reflected from the articles may be gathered by a suitable optical system. The light is converted into electrical signals representing the intensity of the reflected color wavelengths and classification occurs on that basis. Examples of bichromatic sorting apparatus include U.S. Pat. No. 3,980,181 (Hoover et al.), U.S. Pat. No. 4,088,227 (Lockett) and U.S. Pat. No. 4,134,498 (Jones et al.) each assigned to the assignee of the present invention. The apparatus disclosed in U.S. Pat. No. 2,803,754, U.S. Pat. No. 2,908,375, U.S. Pat. No. 2,908,388, U.S. Pat. No. 2,966,264, and U.S. Pat. No. 3,012,666 (all to Cox), all assigned to the assignee of the present invention, are exemplary of another bichromatic color sorter useful to classify articles (as lemons or other citrus fruits) on the basis of color and reflectivity.
In contrast, to adequately perform a sort for surface blemishes or defects, it is necessary that the entire surface area and not merely a portion thereof be scrutinized. Typically, objects which are examined for surface defects or blemishes usually present a curved surface and exhibit at least one axis of rotation (either spherical or elliptical). As such, these articles are susceptible to rolling and the earliest prior art attempts at surface defect sorting utilized manual labor to rotate the articles over an array of roller elements. As the articles are manually rotated over the rollers, the entire surface area thereof is exposed to the inspection of the laborer, and if a surface blemish or defect appears, the article is removed.
It is apparent that the manual scheme carries with it many drawbacks, among which are the imprecision of the sort, the variance between classifications by laborers, the relatively low throughput and, as labor costs escalate, the relatively high cost. It is not surprising, therefore, that the art sought ways to automatically scan the entire surface of the article and classify the article on the basis of surface defects. One such effort is the apparatus disclosed in U.S. Pat. No. 3,382,975 (Hoover), also assigned to the assignee of the present invention, which relates to an apparatus wherein articles to be sorted (potatoes) are pumped through a column of water past a series of multiple detectors disposed circumferentially about the column.
The concept of individually conveying articles past the scanning and ejecting zones (as exemplified by the last-cited patent) is carried over in other prior art systems. Usually sorting systems wherein the articles are individually conveyed require extensive mechanical feeding and article orienting systems adapted to provide an array of singulated article streams through the scanning and ejecting zones. Believed typical of such prior art apparatus, wherein roller elements are used to rotate the surface area of the article, is U.S. Pat. No. 4,122,951 (Alaminos). This patent also appears noteworthy for its disclosure of the use of a television camera for generating a video signal concerning the existence of blemishes on the surface of each article in the highly singulated array of articles passing through an observation zone.